Concurrent daytime and nighttime heatwaves in the late 21st century over the CORDEX-East Asia phase 2 domain using multi-GCM and multi-RCM chains

Abstract

The adverse impacts of extreme heat on human health are greater when concurrent daytime and nighttime heatwaves (CDNHWs) occur than when daytime or nighttime heatwaves occur individually, due to reduced recovery time from heat exposure. This study projects future changes in CDNHWs across East Asia under RCP2.6, RCP8.5, SSP1-2.6, and SSP5-8.5 scenarios. Daily maximum and minimum temperatures are derived from 3-hourly temperatures at 25-km resolution produced by 12 GCM-RCM chains participating in CORDEX-East Asia Phase 2. During the historical period (1981-2005), the East Asian mean CDNHW occurrence period and rate from April to September are 10.9 days and 0.9 percent, respectively. By 2071-2100, they increase to 3 weeks and 3.7 percent under RCP2.6, 2 months and 20.5 percent under RCP8.5, 2 months and 15.6 percent under SSP1-2.6, and 3 months and 45.7 percent under SSP5-8.5. CDNHW intensity and spatial extent also increase substantially. The proportion of CDNHWs lasting more than 10 days increases from 0.2 percent historically to 1.2 percent, 7.2 percent, 6.1 percent, and 17.3 percent under RCP2.6, RCP8.5, SSP1-2.6, and SSP5-8.5, respectively. Particularly large increases in CDNHW occurrence and intensity are projected over Indochina, East and West China, and India. Under continued high greenhouse gas emissions, East Asia is expected to experience unprecedented heat stress as CDNHWs become substantially more frequent and intense by the end of the 21st century.